This is a mod designed to ease the work of mappers, by giving them more possibilites. If you've never designed maps, you'll barely notice the effect of the mod (especially if you played other FPSes like Duke Nukem 3D) but as a mapper I'm sure you'll find the new options very useful. This does not mean that averge players shouldn't get the mod - vice versa. In order to play the new exciting maps people will build with this mod, you'll need to install it. So do so. NOW.